Asteroseismology and the Time Domain Revolution in Astronomy Marc Pinsonneault Ohio State University Collaborators: The APOKASC team Melissa Ness Marie Martig

The Need for Precision Stellar Astrophysics Stars are important across a wide range of astrophysics Origins Questions –Planet Formation –Structure Formation Complex Observational Patterns: Things Move!  Precise Data Needed  Need Better Stellar Physics

Kepler mission: 160,000 stars monitored

Waves are Generated by Turbulence in Stars

Two Major Impacts of Asteroseismology We can measure fundamental properties (mass, radius, age, rotation) in bulk stellar populations Extremely precise surface gravities are a natural product We have entirely new categories of stellar observables –Surface CZ depth –He ionization –Core rotation –Core mass and density Spectroscopy + Asteroseismology 2Gether 4Ever

Solar-like Oscillations in Kepler 16 Cyg A Metcalfe et al Pure p-mode pattern max Rotational Splittings

The observed oscillation pattern is a strong function of log g From Chaplin & Miglio 2013

Giants and Kepler Giants are high-amplitude pulsators –Periods of days to months Long period is a huge advantage  Accessible with 30 minute cadence  16,000 stars monitored, essentially all detected (Mosser et al. 2009; Hekker et al. 2010) Observed frequency pattern is complex!

Giant and Dwarf Frequency Patterns Compared CM 13

The Complex Giant Pattern is Explained by Mixed Modes Mixed modes propagate as p-modes in the convective envelope and g-modes in the deep core; especially strong impact on l=1 l=0 modes are pure p-modes l=0 modes are pure p-modes Seen in red giants (Bedding et al. 2010) because the p and g mode frequencies become commensurate Comparing the two yields distinct diagnostics of core and envelope properties

Distinct Patterns in Different Evolutionary States Dwarf Subgiant RGB RC CM 13

Scaling Relations for Bulk Populations Two most basic observables: –Frequency of maximum power –Mean frequency spacing Hekker et al data for Kepler giants

Radius and Mass Scaling in Clusters Discrepancy for clump giant radii relative to RGB radii (~0.05) tied to structural properties Small but real mass difference Msun, RGB vs. that expected from EB constraints on the MS (Brogaard et al. 2012) Miglio et al. (2012)

Epstein et al. (2014) Trouble In Halo-Land Halo Star Masses From SR Are Well Above Expected Values….

Beyond Scaling Relations: Towards Reliable Masses Boutique Modeling: Reasonable Mass! Parallax+  : Reasonable Mass! Gaia will have a huge impact Calibrate…Correct…OR

Two Paths Forward Boutique Modeling Use the full information in the frequency spectrum Use absolute frequencies for evolutionary state Replace nu(max) with g- mode spacings Add in proper modeling of mean density Parallax Über Alles  + Fluxes+ T eff = R Add in proper modeling of mean density Profit!

APOGEE at a Glance The Apache Point Observatory Galactic Evolution Experiment Operates in the near-infrared (H band):  m Targeted ~10 5 RG stars sampling the bulge, disk(s), and halo(es) DR10 (Ahn et al. 2014): [M/H], [a/Fe] DR11-12 (Alam et al. 2015) 15 Element Mix (C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, Ni) More numbers! S/N = 100+/pixel R ~ 22,500 ~230 science fibers, 7 deg 2 FOV RV precision: ~ 100 m/s Abundance precision: <0.1 dex S. R. Majewski

APOKASC Summarized ORIGINAL KEPLER FIELD Dwarfs: Kepler Field Control –~2,000 (AU 2015) –~7,000 (SU 2016) Giants: Population Asteroseismology –DR10: 1,916 (Pinsonneault et al. 2014) –DR11+12: ~8,000 (AU 2015) –DR13: ~16,000 (SU 2016) Targeting Criterion: H<11 (1 hour exposure) T eff < 5500 K

Automated Pipeline Analysis Boutique analysis of 100,000 targets…NO. Automated fitting algorithm (FERRE) for the entire H band spectrum Ex post facto calibration of results against independent measurements –Star cluster members –Asteroseismic log g

Calibrating the Pipeline: Temperatures Meszaros et al. (2013) Star Cluster Data Holtzman et al. (2015) Low Reddening Photometric Temperatures

Calibrating the Pipeline: Surface Gravity Meszaros et al. (2013): Cluster Star + asteroseismic log g Holtzman et al. (2015) Pure asteroseismic log g

Calibrating the Pipeline: Metallicities Meszaros et al. (2013) Holtzman et al. (2015)

New: 15 Element Mixture Individual Elements fit with a limited line list calibrated vs. cluster stars

APOGEE: 100,000 Red Giant Spectra

The APOKASC Approach APOGEE sample: 1916 stars that pass quality control checks Extract mean asteroseismic properties ( , max ) Scaling relations + grid-based modeling Pinsonneault et al. 2014

Results: Snapping Into Focus Photometry Spectroscopy Asteroseismology + Spectroscopy Pinsonneault et al. 2014

Mass Trends, Fixed [Fe/H]

Metallicity Trends, Fixed Mass

A Test of Atmospheres The difference between asteroseismic and spectroscopic log g is different for RC, RGB Is this an atmospheres or asteroseismic systematic?

One Size Does Not Fit All Macroturbulence is very different in the clump and RGB  Different line broadening  Impacts gravities Massarotti et al. 2008

Testing the Assumptions of Chemical Tagging Martig et al % of high [  /Fe] stars are young (or mergers)

…Invisible to Traditional Surveys

On the Way: Much larger  -rich, metal- poor samples

New in 2015: Richer Phase Space Coverage

Much Larger Sample Size

The Future of Large Spectroscopic Surveys? Ness et al. 2015a “Cannon” Compare Spectra to Empirical Calibrators, Not Directly to Models

From Spectra to Mass and Age Surface C/N, C 12 /C 13 are strongly related to mass through 1 st dredge-up => Spectroscopic Mass labelling of red giants! Martig et al. 2015b

An Age Map of the Red Clump… Asteroseismic Masses Inferred From Spectra (Ness et al. 2015b)

…Across the Galaxy Ness et al. 2015b

Kepler Rebooted: K2 The New Kepler Mission: Step and Stare in the Ecliptic Plane Strong overlap with APOGEE fields; opportunity for sampling a wide range of stellar populations -TESS; PLATO;…..

Future: SDSS-4 + K2 SDSS-4: Two spectrographs (north and south) K2 – numerous APOGEE targets already in fields, used for targeting. 10,000+ fibers reserved for K2 targets